This invention relates in general to laminated structural panels and more particularly to a laminated foam panel which is especially well suited for use as a bulkhead to partition a cargo compartment in a trailer or other cargo container.
Large over the road trailers are often partitioned into two or more cargo compartments which at times must be maintained at different temperatures and/or different humidity levels. For example, if ordinary cargo is carried along with produce and frozen goods in the same trailer, the cargo compartment must be partitioned into one compartment which is maintained below freezing for the frozen goods, another compartment which is maintained above freezing but below the ambient temperature for the produce, and a third compartment which can be at ambient temperature and humidity. In other situations, the cargo compartment must be partitioned simply to keep different types of cargo separated.
Normally, the function of partitioning the cargo area is performed by adjustable bulkheads that are installed in the trailer and can be adjusted along its length. The bulkhead contains thermal insulation if it is to serve as a barrier in a refrigerated cargo compartment.
The bulkhead is typically constructed of insulating material which is held in a rigid metal frame and covered on both sides by sheet metal or sheets of fiberglass reinforced plastic. Although this type of bulkhead functions well for the most part, it is relatively expensive to manufacture and is also somewhat heavy because of the amount of rigid materials that are required for structural purposes. In addition, if excessive loads are applied to the bulkhead by shifting cargo or other forces, the frame can be permanently bent or the insulation can be broken or otherwise damaged and this essentially destroys the bulkhead.
The present invention is directed to a laminated structural panel which is well suited for a variety of applications and particularly for service as a bulkhead which acts as a load restraint in a cargo compartment. The invention deals additionally with a method by which the laminations of the panel are attached and assembled.
In accordance with the invention, resilient structural foam such as open cell polyurethane foam is used to provide a core panel. Flexible plastic sheets are adhesively bonded to opposite sides of the core panel in order to reinforce and enhance the structural properties of the foam. One or more additional layers of foam are adhesively bonded to both sides of the core laminate, and the outer foam layers perform several functions. They enhance the already substantial beam and column strength of the panel and also protect the central core from damage due to impacts caused by shifting cargo or other externally applied forces. The opposite sides of the panel are covered by puncture and abrasion resistance skins which are adhesively bonded to the outer layers of foam.
The laminated panel exhibits good beam strength primarily because the reinforcing sheets are strong in tension and at least one of them must be stretched before the panel can deflect as a result of loads supplied perpendicular to its surface. For the same reason, buckling of the panel due to column loading is resisted primarily by the reinforcing sheets. The multiple layers of foam provide thermal insulation and sound dampening, and their resilience causes the panel to revert to its original flat shape rather than to permanently fail after it has been deflected due to application of a load. The reinforcing sheets and skins spread applied forces over relatively large areas and provide dimensional stability to the panel as well as acting as vapor barriers.
The characteristics of the laminated panel make it particularly useful for service as an adjustable bulkhead for partitioning the cargo area of a trailer compartment or other cargo compartment. The beam strength of the panel, the resistance to puncture and abrasion provided by the outer skins, and the impact protection provided by the multiple layers of foam all contribute to the ability of the panel to stand up under the loads that are applied by typical cargos carried in trailers. The resilience of the foam and the column strength of the panel are effective to maintain the bulkhead sealed continuously around its perimeter, and the thermal insulating characteristics of the foam make it resistant to heat transfer and thus well suited for use in refrigerated trailers.